(1) Field of the Invention
This invention generally relates to an exhaust gas cleaning device for diesel engines of motor vehicles and more particularly relates to a device having filter means capable of physically catching carbon particles or the like (hereinafter referred to as exhaust particles) contained in the exhaust gas and means for burning and removing periodically the caught exhaust particles, thereby regenerating the capability of the filter means.
(2) Description of the Prior Art
Exhaust particles in the exhaust emissions of diesel engines contain considerable amounts of combustible substances, such as carbon particles or the like, as well as other harmful substances. Hitherto, various kinds of devices have been proposed and used for catching such combustible particles by using an appropriate filter element and then burning and removing the caught particles in order to regenerate the capability of the filter element. Especially, a method is conventionally known for providing electric heaters on the surface of the filter material to ignite the exhaust particles attached thereto and to introduce the energy thus released to the inside area of the filter to burn the exhaust particles accumulated therein.
In a conventional exhaust gas cleaning device having electric heaters, the heating elements are directly attached to the upstream end face of the filter member in order to easily burn the exhaust particles accumulated therearound. Under such an arrangement of the heater elements, when the trap case is subjected to engine vibration, since the trap case is directly connected to the exhaust pipe of the engine and therefore the engine vibration is easily transmitted thereto, the heating elements and the front face of the filter may scrub each other, which results in all of these elements being worn. Finally, the heating elements may be broken or a considerable gap may be formed between the heating elements and the front face of the filter, which makes the burning of particles difficult under the preset power, since the preset power is predetermined on the basis of the condition that the heating elements always contact the filter material.